All right, all right -- please rename the file named "master-password" in your domain's folder to something else. It should then prompt you for the master password. If not, on the start-domain command, provide a file as: asadmin start-domain --user admin-user-name --passwordfile filename domain-name" where filename contents are:
AS_ADMIN_PASSWORD=admin-password (the one you use for GUI)
AS_ADMIN_MASTERPASSWORD=changeit (this is the vanilla domain's default keystore password).